Highly fluorinated ion exchange polymers are well known for use in making membrane separators for electrochemical cells. Such cells typically employ a membrane of ion exchange polymer which serves as a physical separator between the anode and cathode while also serving as an electrolyte. Cells with membrane separators can be operated as electrolytic cells for the production of electrochemical products or they may be operated as fuel cells for the production of electrical energy.
Highly fluorinated, and particularly perfluorinated, ion exchange polymer membranes are well suited for use in electrochemical cells due to excellent chemical resistance, long life, and high conductivity. However, membranes of such polymers do not have a high tensile strength. Moreover, the membranes during use must have a certain water content to be conductive and, in some applications, are in contact with aqueous solutions. The membranes typically swell under such conditions which further decreases tensile strength. Accordingly, for some applications, such as chloralkali electrolytic cells, it is necessary for the membranes to be reinforced with fabrics to provide the required strength. For other applications such as fuel cells, unreinforced polymer is adequate to provide the required strength when the membranes have a thickness of at least about 50 .mu.m. However, increased strength is desired, especially to facilitate handling during manufacture and in end use processing operations. Membranes with increased tensile strength but without woven reinforcements are desired, particularly very thin, high performance membranes.
Highly fluorinated nonfunctional polymers are particularly useful for applications which experience weathering, harsh chemicals or other severe conditions. However, since they also have a very low surface energy, it is difficult to get such polymers to adhere to substrates. Highly fluorinated polymers with improved adhesion properties are desired for some applications.